1. Field of the Invention
The invention relates generally to the field of chemical treatment systems for use with hydrocarbon producing wells. More specifically, the invention relates to chemical treatment systems which inject chemicals into the well.
2. Background Art
Chemical treatment systems are used in hydrocarbon producing wells to introduce various chemicals into such wells to, for example, control or prevent buildup of scale from water produced from subsurface formations, reduce or remove solid hydrocarbon deposits and to inhibit corrosion of metal components in the wellbore, among other purposes. Chemical treatment systems known in the art include chemical pumps that withdraw chemical from a storage tank and introduce the treatment chemical(s) into the wellbore.
One device known in the art for providing controllable, continuous chemical treatment for well production equipment is disclosed in U.S. Pat. No. 5,209,300 issued to Ayres. An apparatus and method described in the Ayres '300 patent include a vessel which holds the chemical and a pressurized gas which exerts a pressure on the chemical. A pressure regulator and a valve selectively control the injection of the chemical into the well as the pressurized gas urges the chemical out of the vessel. The pressurized gas drives the chemical through the regulator, valve, and into the well without venting the chemical or pressurized gas into the ambient environment. The apparatus described in the Ayres '300 patent is adapted to inject chemicals into the well in essentially undiluted form. Another chemical treatment system known in the art is described, for example in U.S. Pat. No. 7,721,806 issued to Ayres.
Chemical treatment systems known in the art dispense a selected amount of chemical with each treatment cycle by operating a valve to release chemical under pressure, or by operating an injection pump. The valve of pump may be operated for a selected period of time, either by an electromechanical timing device, an electronically programmed controller, or by signals conducted to a controller from a flow meter or similar device to measure the amount of chemical moved from a storage tank to the well. It has been observed that accuracy of such devices when dealing with small total volumes, yet at relatively high flow rates may be inadequate. Further, an amount of chemical remaining in the storage tank is typically indicated by a visual indicator, such as a sight glass. Thus, the amount of chemical may be insufficient or excessive for any particular well, and it is typically necessary for a human operator to observe the indicator to determine when it is necessary to refill the storage tank with chemical. What is needed is a system to more accurately determine the amount of treatment chemical dispensed into a wellbore, and to provide indication of an amount of chemical in the storage tank that may be interrogated remotely.